1. Field of the Invention
The present invention relates to an optical density changing element, an optical element equipped with such optical density changing element, and a photographing unit equipped with such optical element.
2. Description of the Related Art
An electrochromic material is known as a material showing a change in an optical density in response to an electromagnetic wave. The electrochromic material shows a reversible change in the optical density by an electron transfer, and is generally utilized as a material for an automotive antiglare mirror and a light regulating window.
It is reported that such electrochromic material, when adsorbed on a set of electrodes (anode and cathode), functions as an optical density changing element of a fast response speed (for example JP-T No. 2000-506629 and JP-T No. 2003-511837, and Journal of Physical Chemistry B, Vol. 104, 11449 (2000)).
Such optical density changing element is constructed by forming a layer of a semiconductor material (for example titanium oxide or antimony-doped tin oxide) of a nano-sized porous structure on the surface of a set of electrodes, adsorbing an electrochromic material in such layer and arranging such set of the electrodes in a mutually opposed relationship across an electrolyte liquid.